[libc-commits] [libc] [libc] implement mkstemp (PR #199220)

[Michael Jones via libc-commits]

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@@ -0,0 +1,70 @@
+//===-- Implementation of mkstemp -----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdlib/mkstemp.h"
+#include "hdr/errno_macros.h"
+#include "hdr/fcntl_macros.h"
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/getrandom.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/open.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/null_check.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, mkstemp, (char *tmpl)) {
+  LIBC_CRASH_ON_NULLPTR(tmpl);
+
+  cpp::string_view str_view(tmpl);
+  size_t count = 0;
+  size_t len = str_view.size();
+
+  for (size_t i = len; i > 0; i--) {
+    if (str_view[i - 1] != 'X')
+      break;
+    count++;
+  }
+
+  if (count < 6) {
+    libc_errno = EINVAL;
+    return -1;
+  }
+
+  char *suffix = tmpl + len - count;
+
+  const char charset[] = "QWERTYUIOPASDFGHJKLZXCVBNM"
+                         "qwertyuiopasdfghjklzxcvbnm"
+                         "1234567890"
+                         "._-";
+
+  while (true) {
----------------
michaelrj-google wrote:

The actual loop condition is that the file has not yet been created. Instead of using `while(true)` I'd recommend creating a `bool file_created` variable which starts as `false`. Then when the file is detected as successfully created it can be set to `true`. That way you can move the `return fd.value()` outside the loop, which will make control flow easier to understand.

https://github.com/llvm/llvm-project/pull/199220